#include "elna/lexer.hpp"

namespace elna
{
    source::source(const std::string& buffer)
        : m_buffer(buffer)
    {
    }

    source::const_iterator source::begin() const
    {
        return source::const_iterator(std::cbegin(m_buffer));
    }

    source::const_iterator source::end() const
    {
        source_position end_position{ 0, 0 };

        return source::const_iterator(std::cend(m_buffer), end_position);
    }

    source::const_iterator::const_iterator(std::string::const_iterator buffer,
            const source_position start_position)
        : m_buffer(buffer), m_position(start_position)
    {
    }

    const source_position& source::const_iterator::position() const noexcept
    {
        return this->m_position;
    }

    source::const_iterator::reference source::const_iterator::operator*() const noexcept
    {
        return *m_buffer;
    }

    source::const_iterator::pointer source::const_iterator::operator->() const noexcept
    {
        return m_buffer.base();
    }

    source::const_iterator& source::const_iterator::operator++()
    {
        if (*this->m_buffer == '\n')
        {
            this->m_position.column = 1;
            ++this->m_position.line;
        }
        else
        {
            ++this->m_position.column;
        }
        std::advance(this->m_buffer, 1);

        return *this;
    }

    source::const_iterator& source::const_iterator::operator++(int)
    {
        auto tmp = *this;
        ++(*this);
        return *this;
    }

    bool source::const_iterator::operator==(const source::const_iterator& that) const noexcept
    {
        return this->m_buffer == that.m_buffer;
    }

    bool source::const_iterator::operator!=(const source::const_iterator& that) const noexcept
    {
        return !(*this == that);
    }

    token::token(const type of, source::const_iterator begin, source::const_iterator end)
        : m_type(of), m_value(begin, end)
    {
    }

    token::type token::of() const noexcept
    {
        return m_type;
    }

    const token::value& token::identifier() const noexcept
    {
        return m_value;
    }

    const source_position& token::position() const noexcept
    {
        return m_position;
    }

    result<std::vector<token>> lex(const std::string& buffer)
    {
        std::vector<token> tokens;
        source input{ buffer };

        for (auto iterator = input.begin(); iterator != input.end();)
        {
            if (*iterator == ' ' || *iterator == '\n')
            {
            }
            else if (std::isgraph(*iterator))
            {
                auto current_position = iterator;
                do
                {
                    ++current_position;
                }
                while (current_position != input.end() && std::isgraph(*current_position));
                token new_token{ token::type::word, iterator, current_position };

                tokens.push_back(new_token);
                iterator = current_position;
                continue;
            }
            ++iterator;
        }

        return tokens;
    }
}